西藏札达盆地沉积物的石英砂表面特征及其环境意义

在扫描电镜下对札达盆地香孜组、古格组和托林组地层中的石英砂表面结构特征进行观察, 三个组中石英颗粒外形磨圆度均不好, 以棱角和次棱角状为主, 结合区域地质认为, 盆地的沉积物源距离盆地沉降区很近, 为盆地周围的山地。其中香孜组的上部和中部冰川砂粒表面特征明显, 认为是水体较浅冰缘区河湖相沉积环境; 香孜组下部为湖泊水体较深的冰缘区河湖相沉积环境。古格组石英砂颗粒表面具有溶蚀坑和沟, 属于低化学能的湖相沉积。托林组则表现出河流相沉积的特点。

Quartz grain Surface Characteristics of Sediments from the Zanda Basin of Tibet and Their Environmental Significance

The quartz grain surface structural characteristics of the strata in Xiangzi, Guge and Tuolin Formations of Zanda basin were studied under scanning electron microscope. The quartz grains of the three formations are poorly rounded, and the quartz grains are mainly in sharp-edged and subangular forms. Taking into account regional geology, the authors hold that the sedimentary provenance of the basin was very close to the basin subsidence area, being the mountainous area surrounding the basin. The sand surface of Upper and Middle Xiangzi Formation shows clear glacial characteristics, suggesting that the sedimentary environment was a shallow water periglacial river-lacustrine area. The existence of corrosion pits and trenches in the grains suggests that the sedimentary environment of Lower Xiangzi Formation was a deeper water periglacial river-lacustrine area. The quartz grain particle surface of Guge Formation assumes low chemical energy of lacustrine facies. The surface of quartz grain in Tuolin Formation shows characteristics of fluvial sedimentary facies.